class NullObject:
    """万能空对象，任何属性访问返回 None，但在条件判断时为 False"""
    def __getattr__(self, name):
        return None

    def __bool__(self):
        return False

    def __repr__(self):
        return "<NullObject>"

    def __len__(self):
        return 0

NULL_OBJECT = NullObject()